The need for evaluating the integrity of structural material has long been a time-consuming process involving individual point sampling or a complicated series of tests resulting in significant down-time of the structure and most likely incurring damage to the structure.
For example, refractories are large brick, ceramic or composite blocks used to line kilns and furnaces of metallurgical plants which eventually wear gradually introducing defects to the structure. These defects are usually found on the interior or opposing side(s) of the structure and must be assessed in order to obviate further structural damage to the furnace which would otherwise require investment of money and time to repair.
Typically, during conventional testing of, for example, a refractory, a bar is lowered into the furnace to measure the exact depth, inferring thickness of the refractory, and core samples or samples of solidified metal are extracted from the base of the furnace to measure thickness, locate delaminations and test strength and elastic properties. This method is both time consuming and contributes to further damage of the structure. Similar problems exist for several applications, such as road and pavement material, tunnel linings and concrete shafts, etc.
Moreover, conventional testing of structural material integrity involves human intervention to ensure proper contact between the evaluation device and the substrate of the structure material. This is specifically undesirable when testing must occur in hazardous conditions such as in nuclear power plants, or the like.
Other methods of non-destructive analysis of the material of a structure have been contemplated as, for example, in U.S. Pat. No. 4,782,701, Procter. This patent teaches an acoustic emission transducer directly relating a specific physical quantity, such as tangential displacement, to dynamic displacement inferred from the voltage output of the system disclosed. Briefly, tangential motion of the sensing transducer for this system produces a voltage-time output that closely matches calculated time function for the tangential component of the surface displacement. However, this method requires physical contact of both the surface to be analyzed and the measuring device. Further inherent difficulties with this methodology include interfering acoustic signals which involves time-consuming calibration of the transducer and polarization of the electrode system.
Another method of non-destructive analysis considered is based on U.S. Pat. No. 5,983,701 Hassani et al. This method involves the use of a portable miniature seismic reflection system (referred to as an MSR) which analyzes geometrical material structures. The basic principle of acoustic measurement is carried out using an impact source striking the surface of the material to be analyzed and transducers as sensors detecting reflected signals from an interface of the structure. Once again, direct physical contact between the analyzing apparatus and the surface of the structure material must be established in order to achieve the desired results.
The methods noted above are particularly suitable for structures which are readily accessible. It should be noted that these methods do not contemplate the need for analyzing structures which are not readily accessible, such as refractory linings of furnaces. Moreover such methods are not readily adaptable for dangerous and uninhabitable areas, such as nuclear power plants.
Thus, the present invention provides for a method of assessing the integrity of the material of a structure without requiring direct contact with the structure making it possible to assess material or locations which are generally difficult or dangerous to access. Environment conditions, such as heat, are no longer a factor as opposed to conventional methods. It is also possible with the present invention to significantly reduce, if not eliminate, damage incurred during conventional testing.